Hot-gas reciprocating engine with cooled rolling diaphragm seal



Feb. 3, 1970 R. J. MEIJER & 1

HOT-GAS RECIPROCATING ENGINE WITH COOLED ROLLING DIAPHRAGM SEAL Filed May 29, 1968 2 Sheets-Sheet 2 ll lll I I! INVENTOR. ROELF ..LMEIJER GENT United States Patent O 7829 It. Cl. F03g 7/06; F01b 33/12; F15b 21/04 U.S. Cl. 60-24 Claims ABSTRACT OF THE DISCLOSUJRE A hot gas engine having a rolling diaphragm seal between the compression piston and the housing and means for cooling the seal by cooling a medium in the buffer space which contacts the compression piston.

The invention relates to a hot-gas reciprocating engine having first and second spaces of van'able Volume, one having a higher mean Operating temperature than'the other. These spaces communicate with each other via a regenerator through which a working medium can flow reciprocally between said spaces. The Volume of these spaces is varied by pistons coupled with driving means and there are provided seals between one piston and a co Operating cylinder wall, and between this piston and the piston 'od of another piston, each seal being bounded on one side by one of the spaces and on the other side by supporting liquid.

Engines of the kind set forth are known. The material of which the rolling diaphragms are made offers a poor resistance to high temperatures because the creep then rapidly increases and the fatigue strength decreases. This implies that the rolling diaphragms have to be cooled. A direct cooling of the rolling diaphragms, for example, by cooling the supporting liquid or by cooling the part of the cylnder wall over which the rolling diaphragms slide downwards, involves great constructional diiculties. Furthermore, the piston-red seal, if any, is located at the center of the piston and can be cooled directly only with great difliculty.

The invention has for an object to provide a hot-gas reciprocating engine, in which the rolling diaphragms are cooled in an effective and constructionally simple manner. For this purpose, the hot-gas reciprocating engine according to the invention is characterized in that each of the said butter spaces communicates via a duct with a further space which contains the same medium as the relevant butfer space, while the communication duct or the further space includes a cooler. In the hot-gas reciprocating engine according to the invention, when the relevant piston is moved, the medium in the buffer space flows alternately into and out of the further space and passes the cooler arranged in the communication duct. Thus, the medium contained in the butter space is satisfactorily cooled. This medium is in direct contact with the relevant piston so that this piston is also cooled by this medium. This results in an effective cooling of the rolling diaphragms co-operating with the relevant piston-like body. The cooler may be arranged in a simple manner in the communication duct and may have a low flow resistance. Since the pressure of the medium in the butter space is generally substantially equal to the mean pressure prevalin g in the working space, which pressure may be of the order of 100 atmospheres, the medium has a comparatively large heat capacity so that it is capable of transferring a large quantty of heat even at comparatively small temperature differences. Due to the high pressure of the medium, both in the piston and "ice in the cooler, a satisfactory heat transfer between wall and medium is ensured.

The invention further relates to a hot-gas reciprocating engine which comprises several working spaces and in which, each of the buffer spaces below the relevant pistons communicates with at least one buffer space below a piston associated with another working space, while each of the communications includes a cooler.

The invention will be described more fully with reference to the drawing.

FIGURE 1 shows a single-cylinder hot-gas engine in which the buffer space communicates with a further space.

FIGURE 2 shows diagrammatically and not to scale a multi-cylinder hot-gas engine in which the butfer spaces communicate with each other.

Referring now to FIGURE 1, reference numeral 1 denotes a cylinder of a hot-gas engine. This cylinder accommodates a piston 2 and a displacer 3. The piston 2 and the displacer 3 are coupled by means of a piston rod 4 and a displacer rod 5, respectively, with a driving gear (not shown) which is adapted to move this piston and this displacer with a relative phase difference. Between the piston 2 and the displacer 3 is located a compression space 6 which communicates through a cooler 7, a regenerator 8 and a heater 10 with an expansion space 14. The heater 10 consists of a crown of pipes 11 joining on the one hand the regenerator 8 and on the other hand the annular duct 12 and of a crown of tubes 13 joining on the one hand the duct 12 and merging on the other hand into an expansion space 14 located above the displacer 3. The engine further has a bumer 15 by means of which heat can be supplied to the heater 10. The seal between the piston 2 and the cylinder wall 1 is constituted by a rolling diaphragm 16 supported by a liquid 17, while the seal between the piston 2 and the displacer rod 5 is constituted by a rolling diaphragm 18 supported by a liquid 19. The liquid-containing spaces 17 and 19 communicate with each other and are continously supplied with liquid by means of a pumping device 20, provision being further made of a regulating device 21 for maintaining a constant pressure difference over the rolling diaphragms 16 and 18. Below the piston 2 is located a butter space 22 which communicates through a duct 23 with a further space 24. The medium in the buffer space and in the further space is subjected to approxi'mately the same mean pressure as the medium in the working space. The communication duct includes a cooler 25. When the piston 2 is moved, medium from the space 22 fiows reciprocally through the communication duct 23 and is then satisfactorily cooled by the cooler 25. This implies that the medium in the space 22, which Contacts a large wall surface of the piston 2 has a low temperature and thus satisfactorily cools the piston 2. Due to the high pressure, the medium has a large heat capacity so that a comparatively large quantty of heat can be transferred even at low temperature dilferences, while moreover a satisfactory heat transfer between medium and wall is obtained. The rolling diaphragms 16 and 18 contact the wall of the piston 2 along a large part of their length so that the rolling diaphragms can also supply heat to the piston 2, as a result of which the temperature of the rolling diaphragms will remain low. Thus, a long life of the rolling diaphragms is ensured. The location of the cooler 25 in the communication duct 23 provides a large constructional freedom so that the cooler arranged in this duct may have a low resistance.

FIGURE 2 shows a four-cylinder hot-gas engine having four cylinders, A, B, C and D, the Construction of which is fully equal to that of the hot-gas engine of FIGURE 1. The buifer spaces 30, 31 of the cylinders A and B communicate with the but-fer spaces 32, 33 of the cylinders C and D through ducts 34 and 36 which include coolers 37 and 40. The pistons 2 of the cylinders A and B and of the cylinders C and D are out of phase with respect to each other by 180 so that the overall Volume of the buffer spaces 30, 31 and of the buffer spaces 32, 33 remains constant, however, the medium constantly floWs from one bufer space into the other and passes the cooler arranged in the ducts 34 and 36 and is strongly cooled. The pistons 2 will be kept at a low temperature by this strongly cooled medium so that the rolling daphragms cooperating with these pistons will also have a low temperature. Under certain conditions, a communication duct including a cooler may be arranged also between the buffer spaces 31 and 32.

It will appear from the foregoing that the invention pro- I vides a particularly simple and effective solution for cooling the rolling diaphragms in hot-gas reciprocating engines.

What is claimed is:

1. A hot gas reciprocating engine including a housing defining a cylinder, at least one set of expansion, compression, and buifer spaces, a pair of compression and dsplacer pistons movableto vary the Volume of said spaces, and a rolling diaphragm seal Secured between the compression piston and the housing, the seal being bounded on one side by said compression space and on the other side by supporting liquid, With fluid medium in the buffer space Contacting said compression piston, the improvement in combinaton therewth comprising a remote chamber defining a further space, duct means which connect the bufer and further spaces and through which said fluid medium is reciprocally flowable; means for cooling said duct and the medium flowing therethrough, whereby the cooled medium contacts and cools the compression piston which in turn cools the seal secured thereto.

2. A hot gas engine as defined in claim 1, the cooperating cylinder, pistons, and spaces thereof beinga first assembly, further comprising a second similar assembly wherein the further space of one assembly is the buffer space of the other assembly.

3. A hot gas engine as defined in claim 1,1wherein the fluid medium is a gas maintained at a pressure of at least 90 atmospheres.

4. A hot gas engine as defined in claim 1 wherein the walls of the compression piston are contacted by th" seals along a substantially large part of its length.

5. A hot gas engine as defined in claim 1, wherein the displacer piston has a rod traversing the compression piston, comprising a further rolling diaphragm seal between the rod and the compression piston.

References Cited UNITED STATES PATENTS 3,318,100 5/1967 Reinhoudt et al 62-6 3,372,624 3/1968 Rietdijk 60-24 X CARROLL B. DORITY, JR., Primary Examiner i i 'U.S. Cl.X.R. 92-60, 83 

